The injury of the anterior cruciate ligament (ACL) resulting in severe damage to the ligament is a common occurrence. The importance of the ACL to the proper function of the knee, including load transmission across the joint and joint kinematics, requires its restoration in ACL deficient knees if normal knee function is to be made possible once again. Some ACL reconstruction surgical procedures have attained wide acceptance. As a result of biomedical studies, as well as information gained in clinical investigations, these procedures have steadily improved. As part of the reconstruction procedure, the ACL or its substitute is pretensioned by a prescribed amount. The amount of this tension as well as the position of knee at which it is applied varies from procedure to procedure. Although tensioning of the ligament is deemed necessary to ensure the ligament's or substitute's participation in the transmission of loads across the knee, too much tension will result in premature failure of the repair. This important aspect of ACL reconstruction is addressed in this project and it is proposed that this will be studied by evaluating the effects of ACL and ACL substitute pretension upon the kinematics and stability of the knee and the forces transmitted through the ligament during knee function.